linux-kernel - Re: [patch] mm, oom: dump stack of victim when reaping failed

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Message-ID: <20200115084336.GW19428@dhcp22.suse.cz>
Date:   Wed, 15 Jan 2020 09:43:36 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch] mm, oom: dump stack of victim when reaping failed

On Tue 14-01-20 15:20:04, David Rientjes wrote:
> When a process cannot be oom reaped, for whatever reason, currently the
> list of locks that are held is currently dumped to the kernel log.
> 
> Much more interesting is the stack trace of the victim that cannot be
> reaped.  If the stack trace is dumped, we have the ability to find
> related occurrences in the same kernel code and hopefully solve the
> issue that is making it wedged.
> 
> Dump the stack trace when a process fails to be oom reaped.

Yes, this is really helpful.

> Signed-off-by: David Rientjes <rientjes@...gle.com>

Acked-by: Michal Hocko <mhocko@...e.com>

Thanks!

> ---
>  mm/oom_kill.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -26,6 +26,7 @@
>  #include <linux/sched/mm.h>
>  #include <linux/sched/coredump.h>
>  #include <linux/sched/task.h>
> +#include <linux/sched/debug.h>
>  #include <linux/swap.h>
>  #include <linux/timex.h>
>  #include <linux/jiffies.h>
> @@ -620,6 +621,7 @@ static void oom_reap_task(struct task_struct *tsk)
>  
>  	pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
>  		task_pid_nr(tsk), tsk->comm);
> +	sched_show_task(tsk);
>  	debug_show_all_locks();
>  
>  done:

-- 
Michal Hocko
SUSE Labs